What is 5th base?

Answer 1

According to the Wikipedia Article on "Baseball Metaphors for Sex" (Now removed)

5th Base is the act of place a hoop earring into ones anus, inserting your testicles, and removing the earring while screaming "Holy s&^*, my balls are in your a$%!"

Legit that's what it said before Wikipedia removed it. So much Win.

Answer 2

1st base-french kissing, 2nd base-Fondling, 3rd base-Oral sex and sexual stimulation by hand(i.e. fingering, handjobs), home run or 4th base-Sex, and

5th base-The Anus of the female or receiving partner is widened with a hoop ring, then the male partner places his testicles inside of his partners anus. the anus is then closed. The testicles can only be removed by excretion by their partner.